Movable structure, sensor module, and method for calibrating sensor module

ABSTRACT

A movable structure includes: a moving part pivoting about a predetermined axis; a sensor module provided at the moving part or at a site interlocked with the moving part; and a control device controlling the moving part and the sensor module. The control device controls the moving part in such a way that the sensor module takes a first attitude, and gives a calibration instruction to the sensor module. The sensor module includes: an inertial sensor; a calibration unit calculating an attitude of the sensor module based on an output signal from the inertial sensor in response to the calibration instruction and generating correction information based on a difference between the calculated attitude and the first attitude; and a correction unit correcting the output signal from the inertial sensor, based on the correction information.

The present application is based on, and claims priority from, JPApplication Serial Number 2019-102236, filed May 31, 2019, thedisclosure of which is hereby incorporated by reference herein in itsentirety.

BACKGROUND 1. Technical Field

The present disclosure relates to a movable structure, a sensor module,and a method for calibrating a sensor module.

2. Related Art

JP-A-2018-168584 describes a technique for calibrating a plurality ofangle sensors in which, when a working machine is made to operate insuch a way that a work point is located at a plurality of referencepoints on a reference line generated using a laser radiator, thepositions of the work points at the plurality of reference points arecalculated and calibration values of an angle conversion parameter, adimension parameter, and a linear parameter are calculated, utilizingthat the calculated positions of the work points at the plurality ofreference points can satisfy the linear equation of the reference line.

However, the technique for calibrating the sensor described inJP-A-2018-168584 needs the laser radiator in order to generate thereference line. Therefore, for example, in an environment where thelaser radiator cannot be used such as when a laser beam is not reflectedwell due to rain or the like, or at a worksite where there is no staffmember who can use a measuring machine such as the laser radiator, thecalibration of the sensor is complicated.

SUMMARY

A vehicle according to an aspect of the present disclosure includes: amoving part pivoting about a predetermined axis; a sensor moduleprovided at the moving part or at a site interlocked with the movingpart; and a control device controlling the moving part and the sensormodule. The control device controls the moving part in such a way thatthe sensor module takes a first attitude, and gives a calibrationinstruction to the sensor module. The sensor module includes: aninertial sensor; a calibration unit calculating an attitude of thesensor module based on an output signal from the inertial sensor inresponse to the calibration instruction and generating correctioninformation based on a difference between the calculated attitude andthe first attitude; and a correction unit correcting the output signalfrom the inertial sensor, based on the correction information.

In the movable structure, the control device may transmit informationabout the first attitude to the sensor module.

In the movable structure, the first attitude may be a predeterminedattitude.

In the movable structure, the control device may control the movingpart, based on the output signal from the inertial sensor corrected bythe correction unit.

In the movable structure, the moving part may be one of a boom, an arm,and a bucket.

A sensor module according to another aspect of the present disclosure isattached to a moving part of a movable structure or a site interlockedwith the moving part, the movable structure having the moving part and acontrol device controlling the moving part, the moving part pivotingabout a predetermined axis. The sensor module includes: an inertialsensor; a calibration unit calculating an attitude of the sensor modulebased on an output signal from the inertial sensor in response to acalibration instruction from the control device and generatingcorrection information based on a difference between the calculatedattitude and a first attitude; and a correction unit correcting theoutput signal from the inertial sensor, based on the correctioninformation.

A method for calibrating a sensor module according to still anotheraspect of the present disclosure is a method for calibrating a sensormodule. The sensor module includes an inertial sensor and is provided ata moving part or a site interlocked with the moving part. The methodincludes: causing a control device to control the moving part in such away that the sensor module takes a first attitude; causing the controldevice to give a calibration instruction to the sensor module; causingthe sensor module to calculate an attitude of the sensor module based onan output signal from the inertial sensor in response to the calibrationinstruction and to generate correction information based on a differencebetween the calculated attitude and the first attitude; and causing thesensor module to correct the output signal from the inertial sensor,based on the correction information.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of a movable structure according to anembodiment.

FIG. 2 shows an example of coupling a sensor module and a control devicetogether.

FIG. 3 shows an example of the configuration of the sensor module.

FIG. 4 shows an example of a first attitude of the sensor module in afirst embodiment.

FIG. 5 shows an example of the configuration of the control device inthe first embodiment.

FIG. 6 is a flowchart showing an example of procedures in a method forcalibrating the sensor module in the first embodiment.

FIG. 7 shows an example of the configuration of a control device in asecond embodiment.

FIG. 8 shows an example of the first attitude of a sensor module in thesecond embodiment.

FIG. 9 is a flowchart showing an example of procedures in a method forcalibrating the sensor module in the second embodiment.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Preferred embodiments of the present disclosure will now be described indetail with reference to the drawings. However, the embodimentsdescribed below should not unduly limit the content of the presentdisclosure described in the appended claims. Not all the componentsdescribed below are necessarily essential components of the presentdisclosure.

1. First Embodiment

1-1. Configuration of Movable structure

FIG. 1 shows an example of a movable structure 1 according to anembodiment. In FIG. 1, a hydraulic shovel, which is an example of aconstruction machine, is shown as the movable structure 1.

As shown in FIG. 1, the movable structure 1 has a movable structure bodyformed of a lower traveling unit 42 and an upper rotating unit 41rotatably installed above the lower traveling unit 42. At the front ofthe upper rotating unit 41, a work mechanism 50 formed of a plurality ofmembers that can pivot in up-down directions is provided. The upperrotating unit 41 is provided with a driver's seat, not illustrated. Thedriver's seat is provided with an operation device, not illustrated, foroperating each member forming the work mechanism 50. The upper rotatingunit 41 is also provided with a sensor module 30 detecting a tilt angleof the upper rotating unit 41.

The work mechanism 50 has, as the plurality of members, a boom 43, anarm 44, and a bucket 45, which are moving parts pivoting aboutpredetermined axes. The work mechanism 50 also has a bucket link 46, aboom cylinder 47, an arm cylinder 48, and a bucket cylinder 49.

The boom 43 is attached to the front of the upper rotating unit 41 insuch a way as to be able to look up and down. The arm 44 is attached toa distal end of the boom 43 in such a way as to be able to look up anddown. The bucket link 46 is attached to a distal end of the arm 44 insuch a way as to be able to pivot. The bucket 45 is attached to a distalend of the bucket link 46 in such a way as to be able to pivot. The boomcylinder 47 drives the boom 43. The arm cylinder 48 drives the arm 44.The bucket cylinder 49 drives the bucket 45 via the bucket link 46.

A proximal end of the boom 43 is supported at the upper rotating unit 41in such a way as to be able to pivot in up-down directions. The boom 43is rotationally driven relatively to the upper rotating unit 41 by theexpansion and contraction of the boom cylinder 47. The boom 43 isprovided with a sensor module 10 c detecting the state of movement ofthe boom 43.

At the distal end of the boom 43, one end of the arm 44 is rotatablysupported. The arm 44 is rotationally driven relatively to the boom 43by the expansion and contraction of the arm cylinder 48. The arm 44 isprovided with a sensor module 10 b detecting the state of movement ofthe arm 44.

At the distal end of the arm 44, the bucket link 46 and the bucket 45are supported in such a way as to be able to pivot. The bucket link 46is rotationally driven relatively to the arm 44 by the expansion andcontraction of the bucket cylinder 49. The bucket 45, interlocked withthe bucket link 46, is rotationally driven relatively to the arm 44. Thebucket link 46 is provided with a sensor module 10 a detecting the stateof movement of the bucket link 46.

The sensor modules 10 a, 10 b, 10 c are removable and attachedrespectively to the bucket link 46, which is a site interlocked with thebucket 45 as a moving part, to the arm 44, which is a moving part, andto the boom 43, which is a moving part. The sensor modules 10 a, 10 b,10 c can detect an angular velocity and an acceleration acting on thebucket link 46, the arm 44, and the boom 43, respectively. The sensormodule 30 can detect an angular velocity and an acceleration acting onthe upper rotating unit 41. In this embodiment, the sensor module 10 ais provided at the bucket link 46 instead of the bucket 45, in order toreduce a physical stress due to an impact applied on the bucket 45.

The movable structure 1 is also provided with a control device 20computing a tilt angle of the upper rotating unit 41 and positions andattitudes of the boom 43, the arm 44, and the bucket 45 forming the workmechanism 50.

The control device 20 controls the boom 43, the arm 44, and the bucket45, which are moving parts, and the sensor modules 10 a, 10 b, 10 c.Specifically, the control device 20 computes the positions and attitudesof the boom 43, the arm 44, and the bucket 45, based on output signalsfrom the sensor modules 10 a, 10 b, 10 c, and computes the tilt angle ofthe upper rotating unit 41, based on an output signal from the sensormodule 30. The control device 20 controls the operations of the boom 43,the arm 44, the bucket 45, and the upper rotating unit 41, based on thecomputed positions and attitudes of the boom 43, the arm 44, and thebucket 45, and the computed tilt angle of the upper rotating unit 41.The computed positions and attitudes of the boom 43, the arm 44, and thebucket 45, and the computed tilt angle of the upper rotating unit 41 arealso used for a display on a monitor device, not illustrated, at thedriver's seat.

The control device 20 gives a calibration instruction to the sensormodules 10 a, 10 b, 10 c and controls the timing of calibrationprocessing on the sensor modules 10 a, 10 b, 10 c, described later.

FIG. 2 shows an example of coupling the sensor modules 10 a, 10 b, 10 c,30 and the control device 20 together. As shown in FIG. 2, the sensormodules 10 a, 10 b, 10 c are coupled in series and can transmit adetection signal to the control device 20. Coupling the sensor modules10 a, 10 b, 10 c in series in this way can reduce the number of wiringsfor transmitting a detection signal within a moving area and can providea compact wiring structure. The compact wiring structure can make iteasier to select a method for arranging the wirings and can reduce theoccurrence of deterioration, damage and the like of the wirings.

1-2. Configuration of Sensor Module

In this embodiment, an X-axis, a Y-axis, and a Z-axis, which are threeaxes orthogonal to each other, are defined for each of the sensormodules 10 a, 10 b, 10 c, 30. The sensor modules 10 a, 10 b, 10 c, 30detect an angular velocity about each of the X-axis, the Y-axis, and theZ-axis, and an acceleration along each of the X-axis, the Y-axis, andthe Z-axis. The X-axes, Y-axes, and Z-axes of the sensor modules 10 a,10 b, 10 c, 30 need not coincide with each other. The sensor modules 10a, 10 b, 10 c have the same configuration. Therefore, in the descriptionbelow, each of the sensor modules 10 a, 10 b, 10 c may be referred to asthe sensor module 10. In this embodiment, the sensor module 30 has thesame configuration as the sensor module 10 described below.

FIG. 3 shows an example of the configuration of the sensor module 10. Asshown in FIG. 3, the sensor module 10 includes an inertial sensor 100, amicrocontroller 110, and a communication interface circuit 120. Theinertial sensor 100, the microcontroller 110, and the communicationinterface circuit 120 are accommodated in a package, not illustrated.For example, the microcontroller 110 and the communication interfacecircuit 120 may be included in a one-chip integrated circuit device, andthe inertial sensor 100 and this integrated circuit device may beaccommodated in the package.

The inertial sensor 100 includes an X-axis angular velocity sensor 101,a Y-axis angular velocity sensor 102, a Z-axis angular velocity sensor103, and a three-axis acceleration sensor 104.

The X-axis angular velocity sensor 101 includes an angular velocitydetection element, not illustrated, which detects an angular velocity,and a detection circuit, not illustrated, which performs amplification,synchronous detection, gain adjustment or the like on a signal from theangular velocity detection element and generates a detection signalcorresponding to the direction and magnitude of the angular velocityabout the X-axis. The detection circuit includes an A/D convertercircuit converting the detection signal into a digital signal. TheX-axis angular velocity sensor 101 is arranged in such a way that thedetection axis of the angular velocity detection element is laid alongthe X-axis. The X-axis angular velocity sensor 101 transmits the digitalsignal outputted from the A/D converter circuit, as X-axis angularvelocity data to the microcontroller 110.

The Y-axis angular velocity sensor 102 has the same configuration as theX-axis angular velocity sensor 101 but is arranged in such a way thatthe detection axis of the angular velocity detection element is laidalong the Y-axis. The Y-axis angular velocity sensor 102 transmits thedigital signal outputted from the A/D converter circuit, as Y-axisangular velocity data to the microcontroller 110.

The Z-axis angular velocity sensor 103 has the same configuration as theX-axis angular velocity sensor 101 and the Y-axis angular velocitysensor 102 but is arranged in such a way that the detection axis of theangular velocity detection element is laid along the Z-axis. The Z-axisangular velocity sensor 103 transmits the digital signal outputted fromthe A/D converter circuit, as Z-axis angular velocity data to themicrocontroller 110.

The three-axis acceleration sensor 104 includes three accelerationdetection elements, and a detection circuit, not illustrated, whichperforms amplification, synchronous detection, gain adjustment or thelike on a signal from each acceleration detection element and generatesa detection signal corresponding to the direction and magnitude of theacceleration about each axis. The detection circuit includes an A/Dconverter circuit converting the respective detection signals about thethree axes into digital signals about the three axes. The three-axisacceleration sensor 104 is arranged in such a way that the detectionaxes of the three acceleration detection elements are laid along theX-axis, the Y-axis, and the Z-axis. The three-axis acceleration sensor104 transmits the digital signals about the three axes outputted fromthe A/D converter circuit, as X-axis acceleration data, Y-axisacceleration data, and Z-axis acceleration data to the microcontroller110.

Also, the X-axis angular velocity sensor 101, the Y-axis angularvelocity sensor 102, the Z-axis angular velocity sensor 103, and thethree-axis acceleration sensor 104 may output a detection signal that isan analog signal, and the microcontroller 110 may convert each detectionsignal into a digital signal.

The microcontroller 110 includes a calibration unit 111, a correctionunit 112, a computing unit 113, and a storage unit 114.

The calibration unit 111 performs calibration processing to make thedirection of each axis of the sensor module 10 and the direction of eachcorresponding axis of the sensor module 30 coincide with each other. Thecalibration unit 111 may perform the calibration processing, forexample, when the control device 20 writes predetermined data via thecommunication interface circuit 120 into a predetermined register, notillustrated, included in the storage unit 114. In this embodiment, acorrespondence between the three axes of the sensor module 10 and thethree axes of the sensor module 30 can be arbitrarily set. For example,the Y-axis, Z-axis, and X-axis of the sensor module 10 may be made tocorrespond to the X-axis, Y-axis, and Z-axis of the sensor module 30.

Specifically, the calibration unit 111 calculates the attitude of thesensor module 10 based on an output signal from the inertial sensor 100in response to the calibration instruction received from the controldevice 20 via the communication interface circuit 120, and generatescorrection information 115 based on the difference between thecalculated attitude and a first attitude. For example, the calibrationunit 111 specifies the direction of gravity based on X-axis accelerationdata, Y-axis acceleration data, and Z-axis acceleration data outputtedfrom the inertial sensor 100, and can calculate the attitude of thesensor module 10, based on the relationship between the X-axis, theY-axis, and the Z-axis, and the direction of gravity.

The correction information 115 may be a rotation matrix for rotating theX-axis, the Y-axis, and the Z-axis while maintaining orthogonalitybetween these axes, for example, in such a way as to make the calculatedattitude of the sensor module 10 coincide with the first attitude. Thecorrection information 115 generated by the calibration unit 111 isstored into the storage unit 114. The first attitude is a basic attitudeof the sensor module 10 in a coordinate system defined by the three axesof the sensor module 30.

FIG. 4 shows an example of the first attitude of each of the sensormodules 10 a, 10 b, 10 c. In FIG. 4, a part of the movable structure 1is illustrated in a simplified manner. In the example in FIG. 4, thesensor module 10 a is provided at the bucket link 46. The sensor module10 b is provided at the lateral side of the arm 44. The sensor module 10c is provided at the lateral side of the boom 43. The Z-axes of thesensor modules 10 a, 10 b, 10 c are laid in the same direction. Thesensor module 30 is provided, for example, at the floor surface of thedriver's seat in the upper rotating unit 41.

In this embodiment, the attitude of the sensor module 30 is defined bythe roll angle about the X-axis, the pitch angle about the Y-axis, andthe yaw angle about the Z-axis. In the example in FIG. 4, the Y-axis,Z-axis, and X-axis of the sensor modules 10 a, 10 b, 10 c are set tocorrespond to the X-axis, Y-axis, and Z-axis of the sensor module 30,respectively. The attitude of the sensor modules 10 a, 10 b, 10 c isdefined by the roll angle about the Y-axis, the pitch angle about theZ-axis, and the yaw angle about the X-axis. In the calibrationprocessing, all of the roll angle, pitch angle, and yaw angle of thesensor module 30 are assumed to be 0°. When the Y-axis, Z-axis, andX-axis of the sensor modules 10 a, 10 b, 10 c coincide with the X-axis,Y-axis, and Z-axis of the sensor module 30, respectively, all of theroll angle, pitch angle, and yaw angle of the sensor modules 10 a, 10 b,10 c are 0°.

In the example in FIG. 4, during the execution of the calibrationprocessing, the boom 43, the arm 44, and the bucket 45 are static in abent state. The first attitude of the sensor module 10 a has a rollangle of 0°, a pitch angle of ϕ1, and a yaw angle of 0°. The firstattitude of the sensor module 10 b has a roll angle of 0°, a pitch angleof ϕ2, and a yaw angle of 0°. The first attitude of the sensor module 10c has a roll angle of 0°, a pitch angle of ϕ3, and a yaw angle of 0°.For example, ϕ1<ϕ2<0<ϕ3 holds. Therefore, the calibration unit 111 ofthe sensor module 10 a generates the correction information 115 tocorrect the roll angle, pitch angle, and yaw angle calculated based onthe output signal from the inertial sensor 100, to 0°, ϕ1, 0°,respectively. The calibration unit 111 of the sensor module 10 bgenerates the correction information 115 to correct the roll angle,pitch angle, and yaw angle calculated based on the output signal fromthe inertial sensor 100, to 0°, ϕ2, 0°, respectively. The calibrationunit 111 of the sensor module 10 c generates the correction information115 to correct the roll angle, pitch angle, and yaw angle calculatedbased on the output signal from the inertial sensor 100, to 0°, ϕ3, 0°,respectively.

Back to FIG. 3, the correction unit 112 corrects the output signal fromthe inertial sensor 100, based on the correction information 115. Forexample, when the correction information 115 is a rotation matrix, thecorrection unit 112 calculates a matrix product of the X-axis angularvelocity data, the Y-axis angular velocity data, the Z-axis angularvelocity data, the X-axis acceleration data, the Y-axis accelerationdata, and the Z-axis acceleration data outputted from the inertialsensor 100, and the rotation matrix, and thus corrects each data.

The computing unit 113 performs predetermined computation based on theX-axis angular velocity data, the Y-axis angular velocity data, theZ-axis angular velocity data, the X-axis acceleration data, the Y-axisacceleration data, and the Z-axis acceleration data corrected by thecorrection unit 112. For example, the computing unit 113 may calculatethe position of the sensor module 10, based on the X-axis accelerationdata, the Y-axis acceleration data, and the Z-axis acceleration data.The computing unit 113 may also compute, for example, the attitude ofthe sensor module 10, that is, the roll angle, the pitch angle, and theyaw angle, based on the X-axis angular velocity data, the Y-axis angularvelocity data, and the Z-axis angular velocity data. When the sensormodule 10 includes, for example, a temperature sensor, the computingunit 113 may correct temperature characteristics of the X-axis angularvelocity data, the Y-axis angular velocity data, the Z-axis angularvelocity data, the X-axis acceleration data, the Y-axis accelerationdata, and the Z-axis acceleration data, based on an output signal fromthe temperature sensor.

The storage unit 114 is implemented by a semiconductor memory, registeror the like and stores various kinds of information necessary for theprocessing by the microcontroller 110. In this embodiment, the storageunit 114 stores the correction information 115. The storage unit 114 mayalso store information about the first attitude received from thecontrol device 20 via the communication interface circuit 120.

The communication interface circuit 120 is a circuit for communicatingdata with the control device 20. The communication interface circuit 120may perform interface processing, for example, according to the SPI(Serial Peripheral Interface) communication standard or the I2C(Inter-Integrated Circuit) communication standard. In this embodiment,the communication interface circuit 120 receives the X-axis angularvelocity data, the Y-axis angular velocity data, the Z-axis angularvelocity data, the X-axis acceleration data, the Y-axis accelerationdata, and the Z-axis acceleration data corrected by the correction unit112, and transmits these data to the control device 20. Thecommunication interface circuit 120 may also transmit data resultingfrom the computation by the computing unit 113 to the control device 20.The communication interface circuit 120 also receives the calibrationinstruction and the information about the first attitude from thecontrol device 20 and outputs these pieces of information to themicrocontroller 110.

1-3. Configuration of Control Device

FIG. 5 shows an example of the configuration of the control device 20.As shown in FIG. 20, the control device 20 includes a microcontroller210 and a communication interface circuit 220.

The microcontroller 210 includes a calibration instruction unit 211, anattitude setting unit 212, a computing unit 213, and a storage unit 214.

The calibration instruction unit 211 gives a calibration instruction tothe sensor module 10 via the communication interface circuit 220. Thecalibration instruction unit 211 may give a calibration instruction tothe sensor module 10, for example, when an external device, notillustrated, writes predetermined data into a predetermined register,not illustrated, included in the storage unit 214.

The attitude setting unit 212 transmits information about the firstattitude to the sensor module 10 via the communication interface circuit220. The attitude setting unit 212 may transmit the information of thefirst attitude to the sensor module 10, for example, when an externaldevice, not illustrated, writes the information about the first attitudeinto a predetermined register, not illustrated, included in the storageunit 214. The information about the first attitude may also be used asthe calibration instruction. That is, the attitude setting unit 212 mayalso function as the calibration instruction unit 211.

The computing unit 213 receives various data from the sensor module 10via the communication interface circuit 220 and performs predeterminedcomputation based on the various data and work information 215 stored inthe storage unit 214. Particularly, in this embodiment, the computingunit 213 controls the boom 43, the arm 44, and the bucket 45, which aremoving parts, based on the X-axis angular velocity data, the Y-axisangular velocity data, the Z-axis angular velocity data, the X-axisacceleration data, the Y-axis acceleration data, and the Z-axisacceleration data, which are output signals from the inertial sensor 100corrected by the correction unit 112 in the sensor module 10. Forexample, the computing unit 213 may calculate the positions andattitudes of the boom 43, the arm 44, and the bucket 45, based on theX-axis angular velocity data, the Y-axis angular velocity data, theZ-axis angular velocity data, the X-axis acceleration data, the Y-axisacceleration data, and the Z-axis acceleration data, and controls thepositions and attitudes of the boom 43, the arm 44, and the bucket 45 insuch a way that work designed by the work information 215 is carriedout, based on the result of the computation. Thus, the position of theteeth of the bucket 45 is controlled and the work designated by the workinformation 215 is carried out semi-automatically. When the sensormodule 10 computes its own position and attitude and transmits thecomputed position and attitude to the control device 20, the computingunit 213 may control the positions and attitudes of the boom 43, the arm44, and the bucket 45, using this position and attitude.

The computing unit 213 also computes the tilt angle of the upperrotating unit 41, based on the X-axis angular velocity data, the Y-axisangular velocity data, the Z-axis angular velocity data, the X-axisacceleration data, the Y-axis acceleration data, and the Z-axisacceleration data outputted from the sensor module 30, and controls theoperation of the upper rotating unit 41, based on the result of thecomputation. The computing unit 213 may control, for example, thepositions and attitudes of the boom 43, the arm 44, the bucket 45, andthe upper rotating unit 41 in such a way that the work designated by thework information 215 is carried out, based on the tilt angle of theupper rotating unit 41 as well as the positions and attitudes of theboom 43, the arm 44, and the bucket 45.

The computing unit 213 controls the boom 43, the arm 44, and the bucket45, which are moving parts, in such a way that the sensor module 10takes the first attitude, before the calibration instruction unit 211gives the calibration instruction to the sensor module 10. For example,an operator may operate an operation device in such a way that thesensor module 10 takes the first attitude, and in response to thisoperation, the computing unit 213 may control the boom 43, the arm 44,and the bucket 45 to become static in a predetermined state. Also, thecomputing unit 213 may control the boom 43, the arm 44, and the bucket45 to become static in a predetermined state in such a way that thesensor module 10 automatically takes the first attitude, withoutinvolving an operator.

The storage unit 214 is implemented by a semiconductor memory, registeror the like and stores various kinds of information necessary for theprocessing by the microcontroller 210. In this embodiment, the storageunit 214 stores the work information 215 prescribing work to be carriedout by the movable structure 1. The storage unit 214 may also storevarious data received from the sensor module 10 via the communicationinterface circuit 220.

The communication interface circuit 220 is a circuit for communicatingdata with the sensor module 10. The communication interface circuit 220may perform interface processing, for example, according to the SPIcommunication standard or the I2C communication standard. In thisembodiment, the communication interface circuit 220 receives the X-axisangular velocity data, the Y-axis angular velocity data, the Z-axisangular velocity data, the X-axis acceleration data, the Y-axisacceleration data, and the Z-axis acceleration data from the sensormodule 10 and outputs these data to the microcontroller 210. Thecommunication interface circuit 220 also receives the calibrationinstruction and the information about the first attitude from themicrocontroller 210 and transmits these to the sensor module 10.

1-4. Method for Calibrating Sensor Module

FIG. 6 is a flowchart showing an example of procedures in a method forcalibrating the sensor module 10.

As shown in FIG. 6, first, in step S1, the control device 20 controlsthe boom 43, the arm 44, and the bucket 45, which are moving parts, insuch a way that each of the sensor modules 10 a, 10 b, 10 c takes thefirst attitude.

Next, in step S2, the control device 20 transmits information about thefirst attitude to each of the sensor modules 10 a, 10 b, 10 c.

Next, in step S3, the control device 20 gives a calibration instructionto each of the sensor modules 10 a, 10 b, 10 c.

Next, in step S4, the sensor modules 10 a, 10 b, 10 c calculate theirrespective attitudes based on an output signal from the inertial sensor100 in response to the calibration instruction and generate thecorrection information 115 based on the difference between thecalculated attitude and the first attitude.

Finally, in step S5, each of the sensor modules 10 a, 10 b, 10 ccorrects the output signal from the inertial sensor 100, based on thecorrection information 115.

1-5. Advantageous Effects

As described above, in the first embodiment, the control device 20controls the boom 43, the arm 44, and the bucket 45, which are movingparts, in such a way that the sensor modules 10 a, 10 b, 10 c take thefirst attitude, and the control device 20 also gives a calibrationinstruction to the sensor modules 10 a, 10 b, 10 c. The sensor modules10 a, 10 b, 10 c calculate their respective attitudes based on an outputsignal from the inertial sensor 100 in response to the calibrationinstruction, generate the correction information 115 based on thedifference between the calculated attitude and the first attitude, andcorrect the output signal from the inertial sensor 100. Therefore,according to the first embodiment, since the sensor modules 10 a, 10 b,10 c perform calibration on their own based on the information about thefirst attitude transmitted from the control device 20, there is no needto use a measuring machine such as a laser radiator and the calibrationof the sensor modules 10 a, 10 b, 10 c can be performed easily.

According to the first embodiment, the control device 20 transmits theinformation about the first attitude to the sensor modules 10 a, 10 b,10 c. Therefore, the first attitude can be arbitrarily set according tothe arrangement and structure of the moving parts and a high level ofconvenience can be achieved.

According to the first embodiment, the control device 20 controls themoving parts based on an output signal from the inertial sensor 100 andtherefore can control the moving parts with high accuracy.

2. Second Embodiment

A movable structure 1 according to a second embodiment will now bedescribed mainly in terms of different elements from those in the firstembodiment. Components similar those in the first embodiment are denotedby the same reference signs and descriptions similar to those in thefirst embodiment are omitted or simplified. In the description below, asin the first embodiment, the hydraulic shovel shown in FIG. 1 isemployed as the movable structure 1 according to the second embodiment.

FIG. 7 shows an example of the configuration of a control device 20 inthe second embodiment. As shown in FIG. 7, the control device 20 in thesecond embodiment includes a microcontroller 210 and a communicationinterface circuit 220, as in the first embodiment.

The microcontroller 210 includes a calibration instruction unit 211, acomputing unit 213, and a storage unit 214, as in the first embodiment.

The calibration instruction unit 211 gives a calibration instruction toa sensor module 10 via the communication interface circuit 220, as inthe first embodiment.

The computing unit 213 controls the boom 43, the arm 44, and the bucket45, which are moving parts, based on X-axis angular velocity data,Y-axis angular velocity data, Z-axis angular velocity data, X-axisacceleration data, Y-axis acceleration data, and Z-axis accelerationdata, which are an output signal from an inertial sensor 100 correctedby a correction unit 112 in the sensor module 10, as in the firstembodiment. Also, as in the first embodiment, the computing unit 213controls the boom 43, the arm 44, and the bucket 45, which are movingparts, in such a way that the sensor module 10 takes the first attitude,before the calibration instruction unit 211 gives the calibrationinstruction to the sensor module 10.

The storage unit 214 stores various kinds of information necessary forthe processing by the microcontroller 210, for example, work information215 prescribing work and various data received from the sensor module 10via the communication interface circuit 220, as in the first embodiment.

The communication interface circuit 220 receives the X-axis angularvelocity data, the Y-axis angular velocity data, the Z-axis angularvelocity data, the X-axis acceleration data, the Y-axis accelerationdata, and the Z-axis acceleration data from the sensor module 10 andoutputs these data to the microcontroller 210, as in the firstembodiment.

In the second embodiment, unlike in the first embodiment, themicrocontroller 210 does not include the attitude setting unit 212.Therefore, the communication interface circuit 220 receives acalibration instruction from the microcontroller 210 and transmits thecalibration instruction to the sensor module 10 but does not transmitinformation about the first attitude to the sensor module 10.

Although the example of the configuration of the sensor module 10 in thesecond embodiment is similar to FIG. 3 and therefore is not illustratedhere, the sensor module 10 includes, an inertial sensor 100, amicrocontroller 110, and a communication interface circuit 120, as inthe first embodiment. The configuration and functions of the inertialsensor 100 are similar to those in the first embodiment and thereforenot described further here.

The microcontroller 110 includes a calibration unit 111, a correctionunit 112, a computing unit 113, and a storage unit 114, as in the firstembodiment. The functions of the correction unit 112, the computing unit113, and the storage unit 114 are similar to those in the firstembodiment and therefore not described further here.

The calibration unit 111 performs calibration processing to make thedirection of each axis of the sensor module 10 and the direction of eachcorresponding axis of the sensor module 30 coincide with each other, asin the first embodiment. Specifically, the calibration unit 111calculates the attitude of the sensor module 10 based on an outputsignal from the inertial sensor 100 in response to the calibrationinstruction received from the control device 20 via the communicationinterface circuit 120, and generates correction information 115 based onthe difference between the calculated attitude and the first attitude.

As in the first embodiment, the first attitude is a basic attitude ofthe sensor module 10 in a coordinate system defined by the three axes ofthe sensor module 30. However, in the second embodiment, the firstattitude is a predetermined attitude. The calibration unit 111recognizes the first attitude. Therefore, in the second embodiment, thecontrol device 20 does not transmit the information about the firstattitude to the sensor module 10, whereas in the first embodiment, thecontrol device 20 transmits the information about the first attitude tothe sensor module 10.

FIG. 8 shows an example of the first attitude of each of the sensormodules 10 a, 10 b, 10 c in the second embodiment. In FIG. 8, a part ofthe movable structure 1 is illustrated in a simplified manner. In theexample in FIG. 8, the sensor module 10 a is provided at the bucket link46. The sensor module 10 b is provided at the lateral side of the arm44. The sensor module 10 c is provided at the lateral side of the boom43. The X-axes, Y-axes, and Z-axes of the sensor modules 10 a, 10 b, 10c are laid in the same direction, respectively. The sensor module 30 isprovided, for example, at the floor surface of the driver's seat in theupper rotating unit 41.

In the second embodiment, too, the attitude of the sensor module 30 isdefined by the roll angle about the X-axis, the pitch angle about theY-axis, and the yaw angle about the Z-axis. In the example in FIG. 8,the Y-axis, Z-axis, and X-axis of the sensor modules 10 a, 10 b, 10 care set to correspond to the X-axis, Y-axis, and Z-axis of the sensormodule 30, respectively. The attitude of the sensor modules 10 a, 10 b,10 c is defined by the roll angle about the Y-axis, the pitch angleabout the Z-axis, and the yaw angle about the X-axis. In the example inFIG. 8, during the execution of the calibration processing, the boom 43,the arm 44, and the bucket 45 are static in the state of being extendedlinearly, and the first attitude of each of the sensor modules 10 a, 10b, 10 c has a role angle of 0°, a pitch angle of 0°, and a yaw angle of0°. Therefore, the calibration unit 111 of each of the sensor modules 10a, 10 b, 10 c generates the correction information 115 to correct theroll angle, pitch angle, and yaw angle calculated based on the outputsignal from the inertial sensor 100, to 0°.

FIG. 9 is a flowchart showing an example of procedures in a method forcalibrating the sensor module 10 in the second embodiment.

As shown in FIG. 9, first, in step S11, the control device 20 controlsthe boom 43, the arm 44, and the bucket 45, which are moving parts, insuch a way that each of the sensor modules 10 a, 10 b, 10 c takes thefirst attitude.

Next, in step S12, the control device 20 gives a calibration instructionto each of the sensor modules 10 a, 10 b, 10 c.

Next, in step S13, the sensor modules 10 a, 10 b, 10 c calculate theirrespective attitudes based on an output signal from the inertial sensor100 in response to the calibration instruction and generate thecorrection information 115 based on the difference between thecalculated attitude and the first attitude.

Finally, in step S14, each of the sensor modules 10 a, 10 b, 10 ccorrects the output signal from the inertial sensor 100, based on thecorrection information 115.

As described above, in the second embodiment, the control device 20controls the boom 43, the arm 44, and the bucket 45, which are movingparts, in such a way that the sensor modules 10 a, 10 b, 10 c take thefirst attitude, and the control device 20 also gives a calibrationinstruction to the sensor modules 10 a, 10 b, 10 c. The sensor modules10 a, 10 b, 10 c calculate their respective attitudes based on an outputsignal from the inertial sensor 100 in response to the calibrationinstruction, generate the correction information 115 based on thedifference between the calculated attitude and the first attitude, andcorrect the output signal from the inertial sensor 100. Therefore,according to the second embodiment, since the sensor modules 10 a, 10 b,10 c perform calibration on their own based on the first attitude, thereis no need to use a measuring machine such as a laser radiator and thecalibration of the sensor modules 10 a, 10 b, 10 c can be performedeasily.

According to the second embodiment, the first attitude is apredetermined attitude. Therefore, the control device 20 need nottransmit the information about the first attitude to the sensor modules10 a, 10 b, 10 c. The processing load on the control device 20 islighter and the time taken for the calibration processing is shorterthan in the first embodiment.

According to the second embodiment, the control device 20 controls themoving parts, based on the corrected output signal from the inertialsensor 100, and therefore can control the moving parts with highaccuracy.

3. Modification Examples

In the embodiments, the inertial sensor 100 included in the sensormodule 10 detects an angular velocity on three axes and an accelerationon three axes. However, the inertial sensor 100 may detect an angularvelocity on one axis, two axes, or four or more axes and may detect anacceleration on one axis, two axes, or four or more axes. The inertialsensor 100 may also have a sensor other than an angular velocity sensoror acceleration sensor, for example, a temperature sensor or the like.

In the embodiments, the sensor module 10 a is provided at the bucketlink 46, which is a site interlocked with the bucket 45. However, thesensor module 10 a may be provided at the bucket 45. The sensor module10 b, which is provided at the arm 44, may be provided at the armcylinder 48, which is a site interlocked with the arm 44. Similarly, thesensor module 10 c, which is provided at the boom 43, may be provided atthe boom cylinder 47, which is a site interlocked with the boom 43.

In the embodiments, the movable structure 1, where the moving partsprovided with the sensor module 10 or the sites interlocked with themoving parts are the boom 43, the arm 44, and the bucket link 46, isdescribed as an example. However, in the movable structure 1, the numberof moving parts provided with the sensor module 10 or sites interlockedwith the moving parts may be one, two, or four or more.

In the embodiments, a hydraulic shovel is employed as an example of themovable structure 1. However, the movable structure 1 may be any movablestructure having a moving part rotating about a predetermined axis, forexample, a construction machine such as a rough terrain crane, bulldozeror wheel loader, an agricultural machine, or a robot.

The present disclosure is not limited to the embodiments and can becarried out with various modifications within the spirit and scope ofthe present disclosure.

The foregoing embodiments and modification examples are simply examplesand not limiting. For example, the embodiments and modification examplescan be combined together according to need.

The present disclosure includes a configuration substantially the sameas any of the configurations described in the embodiments (for example,a configuration having the same function, method, and effect, or aconfiguration having the same object and effect). The present disclosurealso includes a configuration resulting from replacing a non-essentialpart of any of the configurations described in the embodiments. Thepresent disclosure also includes a configuration achieving the sameadvantageous effect or the same object as any of the configurationsdescribed in the embodiments. The present disclosure also includes aconfiguration resulting from adding a known technique to any of theconfigurations described in the embodiments.

What is claimed is:
 1. A movable structure comprising: a moving part pivoting about a predetermined axis; a sensor module provided at the moving part or at a site interlocked with the moving part; and a control device controlling the moving part and the sensor module, the control device controlling the moving part in such away that the sensor module takes a first attitude, and giving a calibration instruction to the sensor module, the sensor module comprising: an inertial sensor; a calibration unit calculating an attitude of the sensor module based on an output signal from the inertial sensor in response to the calibration instruction and generating correction information based on a difference between the calculated attitude and the first attitude; and a correction unit correcting the output signal from the inertial sensor, based on the correction information.
 2. The movable structure according to claim 1, wherein the control device transmits information about the first attitude to the sensor module.
 3. The movable structure according to claim 1, wherein the first attitude is a predetermined attitude.
 4. The movable structure according to claim 1, wherein the control device controls the moving part, based on the output signal from the inertial sensor corrected by the correction unit.
 5. The movable structure according to claim 1, wherein the moving part is one of a boom, an arm, and a bucket.
 6. A sensor module attached to a moving part of a movable structure or a site interlocked with the moving part, the movable structure having the moving part and a control device controlling the moving part, the moving part pivoting about a predetermined axis, the sensor module comprising: an inertial sensor; a calibration unit calculating an attitude of the sensor module based on an output signal from the inertial sensor in response to a calibration instruction from the control device and generating correction information based on a difference between the calculated attitude and a first attitude; and a correction unit correcting the output signal from the inertial sensor, based on the correction information.
 7. A method for calibrating a sensor module, the sensor module including an inertial sensor and provided at a moving part or a site interlocked with the moving part, the method comprising: causing a control device to control the moving part in such a way that the sensor module takes a first attitude; causing the control device to give a calibration instruction to the sensor module; causing the sensor module to calculate an attitude of the sensor module based on an output signal from the inertial sensor in response to the calibration instruction and to generate correction information based on a difference between the calculated attitude and the first attitude; and causing the sensor module to correct the output signal from the inertial sensor, based on the correction information. 